POWER April 2017 - 32

OPERATIONS & MAINTENANCE
Facilitating Predictive
Maintenance of Electrical Assets
with Pervasive Sensing Strategies
Courtesy: Emerson Automation
Continuous condition-based monitoring of electrical conductors and insulation is an
effective way to reduce required plant maintenance activities, cut operating costs,
and prevent unplanned shutdowns. Collecting data during normal operation can
alert operators to problems in real time.
Jonathan P. Murray
E
lectric utilities strive to improve reliability
in the face of challenges such
as fewer operators, aging assets, and
increased cycling. Critical asset failures resulting
in unplanned shutdowns of power
generation must be avoided as they can cause
lost production, environmental issues, litigation
arising from injuries or fatalities, and
repair and/or replacement of the damaged assets.
Taken together, these issues can amount
to millions of dollars of associated costs.
To address these issues, asset maintenance
is transitioning from traditional reactive and
periodic strategies to proactive strategies,
including continuous condition-based monitoring
of electrical assets. Modern sensing
technology makes it possible to continuously
monitor the health of these assets and
inform plant personnel when-or even before-problems
arise. This article describes
the problem, the causes of asset failures, and
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the various types of sensing systems used to
detect and predict problems in electrical assets
such as switchgear, bus duct, and circuit
breakers.
Common Electrical Asset Issues
It's no secret that downtime can be costly.
Many power plant outages are due to failure
of critical electrical assets. Independent
of the type of power plant, a typical power
delivery system includes assets such as
generators, potential transformers, generator
circuit breakers (GCBs), line disconnect
switches, step-up and step-down transformers,
segregated and nonsegregated bus ducts,
medium-voltage switchgear, and other equipment
needed to support the transmission and
distribution of power.
Electrical assets are subject to overheating
due to excessive loads, normal wear and tear,
and challenging environmental conditions.
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Left unattended, these conditions can lead to
failures or costly damage to the asset and surrounding
equipment, power production loss,
and in extreme cases, severe injury or death.
While diagnosing and detecting all potential
problems in the myriad mix of equipment
(such as generator vibration or transformer
oil deterioration) are important, this article
will concentrate on how to monitor three of
the main sources of electrical failures: overheating
of conductors, insulation breakdown,
and problems related to high levels of moisture.
Excessive
Temperature. Circuit breaker,
bus bar, and cable connections tend to loosen
and/or corrode over time, resulting in thermal
failure of the connection and nearby cable insulation.
Partial
Discharge (PD). As insulators
age, weak spots and defects evolve, and
under certain load conditions, a dielectric
POWER | April 2017
http://www.powermag.com
POWER April 2017

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